This invention generally relates to water jet-propelled boats or watercraft having an inboard motor and an outboard water jet propulsion unit. In particular, the invention relates to apparatus for penetrating a hull of a boat or watercraft with a driven shaft, the input end of the driven shaft being coupled to the drive shaft of an inboard motor and the output end of the driven shaft being coupled to the impeller of a water jet propulsion unit.
It is known to propel a boat or other watercraft using a water jet apparatus mounted to the hull, with the powerhead being placed inside (inboard) the hull. The driven shaft of the water jet apparatus is coupled to the drive shaft of the inboard motor. The impeller is mounted on the driven shaft and housed in a jet propulsion duct or water tunnel or housing.
To facilitate use of water jet-propelled boats in shallow water, it is known to mount the water jet propulsion assembly at an elevation such that the unit does not project below the bottom of the boat hull. This can be accomplished, for example, by installing a duct in the stern of the boat, the duct being arranged to connect one or more inlet holes formed in the bottom of the hull with an outlet hole formed in the transom. The water jet propulsion assembly is then installed outside the hull in a position such that its inlet is in flow communication with the duct outlet at the transom. Alternatively, the water jet impeller can be installed inside the duct built into the hull.
It is further known to integrally form an inlet ramp or tunnel in the stern portion of the bottom of a molded hull. The inlet ramp comprises a pair of opposing side walls which increase in height continuously from a starting point on the hull bottom to the respective points where the side walls join the hull transom. The top edges of the opposing side walls are connected by a ramp ceiling which curves continuously upward. The side walls and ceiling form part of the molded hull bottom and define an inlet channel. Optionally, the junctures connecting the side walls to the ceiling may be formed as rounded, as opposed to sharp, corners. A mounting adapter in the form of a flanged ring having a rounded leading lower lip is mounted to the rear face of the hull transom. The bottom edges of the inlet ramp and the forward tip of the lower lip define an inlet opening for entry of ambient water into the inlet channel formed by the inlet ramp. The mounting adapter is mounted to the transom by fasteners. The water jet propulsion assembly is in turn mounted to the mounting adapter in cantilever fashion in a well-known manner. The outlet of a discharge nozzle of the water jet propulsion assembly is in flow communication with the inlet opening in the hull bottom via the hull inlet ramp, the mounting adapter, and one or more housings of the water jet propulsion assembly itself (e.g., an impeller housing and a stator housing). All of these components, communicating with each other in series, form a duct having a channel with an inlet and an outlet. Rotation of an impeller, driven by an inboard motor, produces flow through the duct in a well-known manner.
In accordance with the latter design, the driven shaft must penetrate the ceiling of the inlet ramp. There is a need for an apparatus or structure which would allow the driven shaft to penetrate the inlet ramp ceiling in a simple and elegant manner without compromising watertightness of the hull. Such a hull penetration apparatus should easy to install and relatively inexpensive to manufacture.
The present invention is directed to a jet-propelled boat having an inboard motor and a hull which incorporates an inlet ramp penetrated by a driven shaft. The driven shaft couples a drive shaft of the inboard motor to an impeller of a water jet propulsion assembly which is mounted in cantilever fashion to the hull transom.
In accordance with the preferred embodiments of the invention, the hull penetration is accomplished by a through-hull housing which is installed in an opening formed in the hull inlet ramp. Preferably the through-hull housing is made of metal (e.g., aluminum), structural plastic or reinforced fiberglass, while the hull is a molded fiberglass and resin laminate. However, the invention also has application in boat hulls made of metal or wood. The through-hull housing comprises a linear bore for passage of the driven shaft through the hull.
In accordance with one preferred embodiment, the through-hull housing comprises a thick plate with a transverse linear bore for shaft penetration and a peripheral flange which seats in a peripheral recess formed along the edge of the opening in the inlet ramp. The recess preferably faces outward from the exterior of the hull. The through-hull housing is clamped to the recessed hull edge, which forms the opening in the inlet ramp, by an annular clamp plate which is preferably installed on the inboard side of the hull. Suitable means are provided to seal against water leaking into the hull via the housing/hull interface.
The preferred embodiment further comprises an inlet grate extending from the outboard surface of the through-hull housing. The inlet grate is preferably a separate component attached to the through-hull housing. This through-hull housing and inlet grate assembly is installed in the hull opening as a module. However, if the housing is made of metal, then the housing and inlet grate may optionally be cast as a single metal component. The inlet grate preferably comprises a plurality of generally parallel cantilever tines extending across at least a portion of the inlet channel for blocking the admission of weeds and/or other debris into the water jet propulsion assembly. However, the present invention is not limited to any particular inlet grate structure or design. Optionally, the inlet grate can be pivotably mounted to the through-hull housing. By pivoting the inlet grate downward. The ends of the tines can be moved to a depth below a lower lip of the mounting adapter, clearing the tine ends of obstruction to allow entangled weeds and other debris to be slid off of the inlet grate during a grate clean-out operation.
In accordance with a further aspect of the preferred embodiment, the outboard end of the linear bore which penetrates the housing has an annular recess of increased diameter for receiving an end of a swaged tube, which is press-fit into the annular recess. This swaged tube extends rearward and is coaxial with the linear bore. In the fully assembled state, the swaged tube surrounds the driven shaft on the outboard side of the hull, the swaged functioning as a shroud for the shaft. The shaft shroud prevents weeds,; ropes or debris from becoming entangled around the rotating driven shaft.
In accordance with another aspect of the preferred embodiment, the through-hull housing comprises a boss penetrated by the linear bore for the driven shaft. A face seal surrounds the driven shaft on the inboard side is effectively anchored to the boss by means of a bellows, also penetrated by the driven shaft. The linear bore is sized to provide sufficient clearance for the driven shaft to rotate freely. The face seal blocks ingress of water into the hull via the linear bore. The anchoring of the seal by means of a bellows accommodates axial displacement and angular misalignment of the driven shaft relative to the linear bore.
In accordance with yet another aspect of the invention, one end of the driven shaft is coupled to the end of the motor drive by means of a shaft coupling which accommodates axial displacement and angular misalignment between the drive and driven shafts.